Math help please?! (using space)

Question

everyday when lisa returns from school she puts her change from buying lunch into a jar on her dresser. this weekend she decided to count her savings. she found that she has 72 coins all nickels and dimes. the total amount was $4.95. how many coins of each kind can she have. come up with two possiblities. explai your process.

please help. ive tryed so hard and its so difficult! thx!

Answer 1

Let N be the number of nickles.

Let D be the number of dimes.

First, we know that

N + D = 72

Secondly, since a nickle is 0.05 dollars and a dime is 0.10 dollars, we know that

0.05N + 0.10D = 4.95

We now have two equations in N and D.  Solve the first for N and plug the result into the second.

N = 72 - D

0.05(72 - D) + 0.10D = 4.95

3.6 - 0.05D + 0.10D = 4.95

0.05D = 4.95 - 3.6 = 1.35

Hence, D = 1.35/0.05 = 27, and N = 72 - D = 72 - 27 = 45

So she has 27 dimes ($2.70) and 45 nickles ($2.25) for a total of $4.95.